题目

向一个半径为2的圆中投掷石子（假设石子全部投入圆形区域内），那么石子落在此圆的内接正方形中的概率是（ ）.A. B. C. D. 答案：【答案】D【解析】先得出圆内接正方形的边长，再用正方形的面积除以圆的面积即可得．∵半径为2的圆内接正方形边长为2，∴圆的面积为4π，正方形的面积为8，则石子落在此圆的内接正方形中的概率是，故选D．We find that bright children are rarely held back by mix-ability teaching. On the contrary, both their knowledge and experience are enriched. We feel that there are many disadvantages in streaming pupils. It does not take into account the fact that children develop at different rates. It can have a bad effect on both the bright and the not-so-bright child. After all, it can be quite discouraging to be at the bottom of the top grade! Besides, it is rather unusual to grade pupils just according to their intellectual ability. This is only one aspect of their total personality. We are concerned to develop the abilities of all our pupils to the full, not just their academic ability. We also value personal qualities and social skills, and we find that mixed ability teaching contributes to all these aspects of learning. In our classrooms, we work in various ways. The pupils often work in groups: this gives them the opportunity to learn to co-operate, to share, and to develop leadership skills. They also learn how to deal with personal problems as well as learning how to think, to make decisions, to analyze and evaluate, and to communicate effectively. The pupils learn from each other as well as from the teacher. Sometimes the pupils work in pairs; sometimes they work on individual tasks and assignments, and they can do this at their own speed. They also have some formal class teaching when this is proper. We encourage our pupils to use the library, and we teach them the skills they need in order to do this efficiently. And advanced pupil can do advanced work. It doesn’t matter what age the child is. We expect our pupils to do their best, not their least, and we give them every encouragement to obtain this goal. 1.By “held back” (the underlined part of the first sentence) the author means “______”. A．drawn to their studies                    B．prevented from advancing C．made to remain in the same class           D．forced to study in the lower class 2.The author argues that a teacher’s chief concern should be the development of the pupil’s ______. A．total personality                        B．intellectual ability C．personal qualities                       D．communicative skills 3.Which of the following is NOT mentioned in the third paragraph? A．Pupils also learn to develop their reasoning abilities. B．Pupils also learn how to participate in teaching activities. C．Group work gives pupils the opportunity to learn to work together with others. D．Group work provides pupils with the opportunity to learn to be good organizers.